The objectives of this research program are 1) to determine the pathogenic mechanisms by which Neisseria gonorrhoeae causes disease and 2) to develop immunologic or other methods for blocking those pathogenic mechanisms. Two major phases of the interaction of gonococci with viable, intact human genital epithelium (fallopian tube mucosa in organ culture) have been defined - the "attachment phase" and the "invasion phase". To investigate the molecular mechanisms of attachment and invasion, techniques have been developed for quantitating attachment of gonococci to human fallopian tube mucosa, for assessing invasion of mucosal cells by gonococci, and for determining the ultrastructural location of specific gonococcal macromolecules using gold sphere-antibody complexes. In the proposed studies gonococcal attachment to human fallopian tube mucosa will be quantitated in the presence or absence of antibodies against antigens on various gonococcal surface macromolecules (e.g., pili, lipopolysaccharide, protein II). This should help determine the molecular mechanisms by which gonococci attach to human genital mucosal cells. Similarly, assessments of phagocytosis performed in the presence or absence of antibodies against gonococcal surface macro-molecules should help determine the mechanisms by which these macromolecules stimulate the invasion process. The use of gold spheres conjugated to these antibodies should allow location of the ultrastructural sites of interaction of these macromolecules with human genital mucosal cells. A number of laboratories are producing antibodies against epitopes on various gonococcal surface macromolecules. The antigens used to produce and detect the antibodies are usually on purified macromolecules (e.g., pilin subunits, protein I). In viable gonococci these antigens are not necessarily accessible for binding to vaccine-elicited antibody. A combination of the techniques described above will be used to determine which parts of which gonococcal surface macromolecules are accessible for interaction with host tissues as part of the disease process and which parts of which gonococcal surface macromolecules are accessible to antibody in viable gonococci. This information, coupled with information on the breadth of cross-reactivity of the antigens identified, should help predict those parts of specific gonococcal macromolecules most likely to be effective as components of a gonococcal vaccine.